Disabling launch_tor timeout when on windows

On windows the python signal module lacks a SIGALRM attribute, breaking
launch_tor. Disabling timeouts on windows to avoid this issue - ideally we
should find an alternative method for timeing out the function on windows but
that can wait.

Caught by pythonirc101. Issue is discussed on...
https://trac.torproject.org/projects/tor/ticket/5783